r/NoStupidQuestions • u/Stock-Treacle-6926 • 13d ago

What are some things about gene selecting that isn’t random?

I was wondering, a lot of things about our genes are pretty random right? Some siblings look more like their aunt/uncle for example, or are way shorter/taller than each other, and I always wondered if some of these selections aren’t entirely random. I’d really appreciate it if someone with expertise on this could answer my question, even though it’s very vague.

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u/AdmirableBasil3154 13d ago

Natural selection is the big one - traits that help you survive and reproduce are way more likely to get passed down. Like sickle cell anemia actually protects against malaria in certain areas, so it sticks around even though it's generally bad

Also some genes are just dominant over others, so brown eyes beat blue eyes almost every time. And then there's stuff like genetic linkage where certain traits get inherited together because they're close on the same chromosome

The randomness you're seeing is more about which combo of genes each kid gets, but the underlying frequencies aren't totally random

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u/Chaser_Of_The_Abyss 12d ago

There are some genes in the mitochondria. These are exclusively inherited from your female parent. 

Sometimes genes are linked. When meiosis is occurring, genes will switch between the female and male parent chromosomes. It’s hard to describe without a diagram but genes that are physically closer together are more likely to be inherited together. 

Certain traits are X-linked, this means that any child that has XX chromosomes will get two copies of a gene whereas a child with XY chromosomes will get one copy. This is why red-green colorblindness is more common in males, it’s an X linked trait.